Thread-tensioning device



Oct. 14, 1930. B. T. LEVEQUE THREAD TENSIONING DEVICE Original Filed Feb. 18} 1927 Patented Oct. '14, 1930 BERNARD 'r. LEVEQU'E, or WENHAM, MASSACHUSETTS, ASSIGNOR "r nm'rnn siren UNITED- STATES PATENT- OFFICE i MACHINERY CORPORATION, OF PATTERSON, NEW JERSEY, ,A CORPORATION OF NEW JERSEY .TI-IREAD-TENSIONING nnvron 7 Original application filed February 18, 1927, Serial No. 169,203. Divided and this application filed March 29, 1928. Serial No. 265,542. f

The present invention relates to thread tensioning devices and more particularly, to a tensioning device for the looking or shuttle thread of a lockstitch sewing machine.

The object of the invention is to provide a simple and efficient tensioning device for the looking or shuttle thread which acts automatically to maintain an even and constant thereby, should be readily understood by one skilled in the art from the following description taken in connection with the accompanying'drawings, in which Fig. 1 is a View in front elevation of the shuttle mechanism in connection with the needle and a portion of the work with the machine parts and the needle and shuttle threads in the positions they assume when they needle is at the limit of its loop drawing stroke; Fig. 2 is a viewin side elevation of the mechanism illustrated in Fig. 1; Fig. 3 is a central sectional view of the shuttle and bobbin case; and Fig. 4 is a'view similar to Fig. 3 withthe bobbin case broken away to show the thread tension plate on the inside wall of the shuttle.

-The drawings illustrate one embodiment of the invention in the lockstitch horn shoe sewing machine more fully described and illustrated in the inventors pending application Serial No. 169,203, of which the present application is a division.

The work engaging devices of the machine comprise a work supporting horn which is adapted to extend within the shoe, a presser foot cooperating therewith, work feeding devices, a straight hook needle, and an oscillating shuttle.

The tensioning device for the shuttle thread which forms more specifically the subj ect-matter of the present invention comprises a spring plate which bears yieldingly against the inner wall of the shuttle case.

The thread passes from the bobbin case around the spring plate where it is held in frictional contact between the. plate and the surface of the shuttle wall, and then back again to a point nearly in line with the axis of the bobbin, from where it passes directly down to the work. With this construction, it is evident that any obstruction or tightening of the feeding thread will tend to pull the spring plate away from the surface of the shuttle walland thus cause a correspond:

ing decrease in the shuttle tension.

Referringmore specifically to the drawings, the straight hook needle is indicated at 6 and the shuttle cooperating therewith at 8. The shuttle is, discoidal in shape and is mounted to reciprocate in a raceway formed in a segmental holding ring 10 removably secured by screws 12 to a correspondingly shaped extensionon a bracket 14 forming a portion of the machine frame.

The tension device for the locking thread comprises a yielding spring plate 16 arranged to press the thread against a cooperating thread support formedby the inner surface of the cylindrical, wall of the shuttle. This thread supporting surface is concentric with and, therefore, parallel to the axis of the shuttle. The plate 16 is held in the shuttle by' meansof holding screws'18 and by an adjusting screw 20 by means of which the tension exerted on the thread may be initially adjusted. The bobbin is supported on a stud 22 projecting from the rear wall of the shuttle and bobbin casecentrally of the bobbin case and the bobbin thread leads from the bobbin through an opening 2 1 in the bobbin case to a guiding notch in the free end of the tension plate 16. The bobbin thread then passes between the tension plate and the thread supporting wall of the shuttleto a second guiding'notch 26 formed in the forward edge of the tension spring. The thread then passes inwardly towards the center of the shuttle and emerges through an opening 28 formed in the bobbin retaining arm 30. 'From the opening 28 the bobbin thread leads to the work. YVith this arrangement of the tension plate, cooperating thread support and thread guides, it will be seen that a pull exerted on the thread leading from the tension plate to the opening 28 and to the work Will tend to swingthe tension plate 16 inwardly away from the thread supporting surface and thereby decrease the frictional resistance offered by the tension plate to the passage of the thread. The result of this arrangement is that the tension on the thread leading from the tension plate to the work is maintained constant regardless ofajnyvariations in the V resistance offered by the thread leading from y the bobbin to the tension plate.

$:laim @1 r a 1' i 1. A lockstitch sewing machine havi ng,:i n I, A combination, a discoidal thread case for the locking-threadhaving provision for support-v ing aibobbin with its axis parallel tothe axis of the thread case, andhavingathread supporting surface on'itsinner wall substantially 29 parallel tothe axis of the bobbin, and a thread tensiondevice arranged tov pressr'the thread outwardly against said surface in its passage. from the bobbin to the work and to yieldinwardly upon an increase in: the resistance 3 ofi'ered by the threadleading from the bob-' bin to said device. I Y

2. A lookstitc'h sewing machine having, in combination, a discoidal thread case ifor'the locking thread having provision for support- 30 ing a bobbin with its axis parallel tothe axis of the thread caseiand having a thread supportingsurface substantially parallel to the axis of the bobbin overrwhich thejthread passes in its passage fromthe bobbin to the 3 work, a tension plate arranged to press the thread against said surface, and means for guiding the thread from the tension plate in a. direction substantially radial'of the thread case to cause the threadto draw the plate 40 away from said surface and equalize the tension upon an increase in the resistance 'ofiered by the thread leading from the bobbin to the plate. 7 a I 3. A lockstitch sewing machine having, in a combination, a discoidal thread case for the locking thread having provision for support -v ing a bobbin with its axis parallel to the axis of the thread case and having a thread sup.- porting surface over which the thread passes in its passage from the bobbin to the work substantially parallel to the axis of the :bobbin and being provided with-a thread delivery opening substantially in line with the axis of the bobbin, and a thread tension device arranged to press the thread yieldinglyoutward against-said surface and tosyield in Wardly upon anincrease in the resistance offered by the thread leading from the bob .7

bin to said devices; 1 V V In testimony whereof'lnhav signed my name to this specification.

. BERNARD T. LE E UEQ The invention having been described, What 

